The invention discloses a preparation method of N-formamide compounds. Carbon dioxide and organic amines are used as raw materials, hydrogen-containing silane is added as a reducing agent, and a 0.1-1.0 mol% salen-type metal complex is used as a catalyst. Under the conditions of 0.1-5.0 MPa and a temperature of 25-100 ° C, with or without adding a co-catalyst, synthesize N-formamide organic compounds; after the reaction, add an organic solvent, centrifuge, separate the catalyst, and pass the supernatant through After the solvent is removed by rotary evaporation, N-formamide compounds are obtained. The preparation method has the advantages of mild reaction conditions, no need to add any organic solvent, simple operation, high catalytic activity, good substrate compatibility, etc., conforms to a green synthesis process, and is suitable for industrial production. In addition, the catalytic system provided by the present invention can be conveniently separated from the reaction system by adding a solvent, so as to realize the recycling of the catalyst.